Relationship Between Chlorophyll Content, Vegetative Traits and Yield - Related Traits in Selected Cowpea Varieties

Abstract

is essential for improving productivity and developing high performing cultivars. This study examined the relationships among chlorophyll content, r,egetative growth parameters and yield-related traits in six cowpea v'arieties (MICPl, M135, ANKCPI, WAR\\NI, DHAWALA and BOMBAY) grown under field conditions using a Randomized Complete Block Design (RCBD) with three replications. Chlorophyll content was quantified using both SPAD meter readings and spectrophotomeffic assays u'hile vegetative traits and leld components were recorded at 5 and 7 weeks after planting. Results revealed clear varietal di{ferences in both ph-vsiological and yield traits . BOMBAY recorded the highest Chlorophyll values. DHAWALA exhibited tlre greatest plant hei-eht and canopy spread whereas MICP I showed the smallest stature but possessed the largest leaf area. Yield performance also differed significantly with ANKCPI achieving the highest grain yield per plant (39.31* 0.53 g) associated with a superior harvest index despite not having the highest vegetative vigor. Correlation analysis indicated a weak and negative association between chlorophyll content and grain yield (r: -0.04) demonstrating that higher chlorophyll content did not predict final productivity. Stomatal obsen'ations further showed varietal differences in gas exchange capacity with WAR(/l/l having higher stomatal density and larger guard cells compaled to the more conservative water-use strategy of ANKCPI. These findings exhibit substantial physiological and yield diversity anong the tested cowpea varieties and identi$r ANKCPI, DHAI'\ULA and BOMBAY as lines of particular interest for future breeding. The findings emphasize that balanced vegetative gro\,th and efficient biomass allocation rather than maximum chlorophyll content alone is the key determinants of cowpea yield urder field conditions in Sri Lanka.